We've featured a lot of roof options, but sorting out which one is best for your home can be like reading Dr. Seuss: green roof, cool roof, metal roof, solar roof... Find out the differences, disadvantages and advantages of each option, and how they can help make your building more green, after the jump.
When designing or rehabbing buildings, roofs are often one of the last items that people attend to — but, they can make one of the biggest environmental impacts on a building and it's surrounding area:
Most roofs that are primarily covered with some type of living vegetation can be considered a green roof. There three primary types: intensive, extensive and trays. Intensive and extensive green roofs are are a permanent vegetative roof. Intensive roofs are thicker, heavier and require the most maintenance, but they are also able to support larger and a wider variety of plants; extensive roofs are more common on large, commercial scale buildings. Intensive roofs are similar to extensive, but they are lighter and thinner, and are more commonly found on smaller scale structures. Green roofs can also be made with containers, or trays filled with vegetated material, which is a non-permanent and less expensive option. Whichever option you choose, make sure that roof is designed to support and maintain a vegetated roof.
Pros: Aesthetically pleasing; reduces, absorbs, and filters rainwater runoff; provides an extra layer of insulation; can act as a vegetable garden; a natural habitat; extends the life of a roof and/or building; can increase the value of the building.
Cons: Initial upfront costs are much higher than a standard roof, and one of the most expensive eco-friendly roof options; requires additional design and engineering review; can be high maintenance; may not be suitable for a retrofit.
In recent months there's been a lot of talk about cool, or also known as, white roofs. Cool roofs are typically made of a light and sometimes reflective material, and have a high solar reflectance — meaning they can reflect visible and infrared light. By having a high solar reflectance, cool roofs are able to keep buildings and their surrounding areas much cooler than a typical dark, matte roof would. Cool roofs can be found in the form of roll on paint, single ply membranes, asphalt shingles and some metal roofs. The Solar Reflectance Index (SRI) rating, which is the measure of a surface's ability to reflect solar heat, is the best way to determine the quality of a cool roof — LEED looks for an SRI of at least 29 for steep sloped roofs and 78 for low sloped roofs (though this will vary by location).
Pros: Reduces building energy use due to lower cooling requirements, reduces the local heat island effect; can be retrofitted in most applications and is relatively affordable.
Cons: Not aesthetically pleasing to everyone; can result in higher wintertime heating costs in cold climates (however this is usually offset by summertime savings).
Most metal roofs have the same advantages of a cool roof, in that they are typically light in color, are reflective and are able to reflect light and heat. The primary outstanding feature of metal roofs is that they are very durable, long lasting, low-maintenance, and made with recycled materials. Metal roofs can be made out of a variety of materials such as copper, steel and zinc, and can come in flat sheet form, corrugated and standing seam.
Pros: Very durable; can withstand fire, heavy rains & winds; made with recycled content; available in a variety of colors, metals and profiles; can also be considered a 'cool roof'; can last much longer than a standard roof; can be appropriate for a variety of building types (traditional, modern and historic); is recyclable at end of life.
Cons: High upfront costs; can be loud due to rainfall; not universally aesthetically pleasing.
One of the major complaints about solar panels is their appearance: they're big, awkward and don't usual fit within the design of a building. But with solar roof shingles, the solar system can be seamlessly integrated into the roof, and in some cases can go completely unnoticed. Solar roofing can come in a variety of shapes and profiles to fit your design needs.
Pros: Shingles can be integrated in roof design and harness the sun's energy for power; can be installed new and retrofit; available in a number of styles and from several manufacturers.
Cons: More expensive than both standard solar panels and standard roofing; may not always be available in design needed.
Other eco-friendly roof options:
(Images as linked above)